Breeding

Andrés Haro & Alvaro Garcia

To achieve their greatest reproductive potential, dairy cows need to conceive as soon as possible after calving. Endocrine changes, referred to as the return to post-partum ovarian activity, occur after uterine involution and function normalization of the hypothalamus-hypophysis-ovarian axis. The use of equine chorionic gonadotropin (eCG) in lactating cows can induce post-partum ovarian activity causing follicle growth to resume.

Alvaro Garcia

In the relatively recent past different devices were developed to monitor estrus. Examples are those that record increased cow activity alone (pedometers), or a combination of the latter with a reduction in intake and rumen motility. Other devices attached to the cows’ back focus on standing mounting behavior by the animals in heat. More recently, there have been devices that have focus on cow vocalization.

Fernando Diaz

Extended lactation, the management practice in which the time of first insemination is delayed deliberately, increases calving interval and reduces the proportion of dry cows in the herd. This changes the lactation curve lengthening the descending phase. Therefore, average daily milk production is reduced in cows with extended lactations.

Using the Danish dairy herd model SimHerd, researchers from Aarhus University, Denmark, compared six different extended lactation strategies with the average Danish conventional Holstein farm in which average calving interval was 13 months. The six extended lactation strategies were managing either all, primiparous or multiparous cows for a calving interval of either 15 or 17 months by setting the time of first insemination to 106 or 166 days in milk, respectively.

Fernando Diaz

Traditionally, the methods used to detect estrus in dairy cows include visual observation, tail painting, tail chalking, rump-based pressure and scratch-off patches. In high-producing cows, the duration and intensity of estrus behavior is considerably lower than that in dairy cows of a few decades ago. In fact, standing estrus only occurs in 30 to 80% of lactating dairy cows. For this reason, precision dairy monitoring devices (tag, leg, collar) that measure cow activity, rumination, and feeding and lying behaviors are commonly used for estrus detection.